A dam that belonged to Brazil's giant mining company Vale burst on Friday. Picture: Douglas Magno/AFPSource:AFP

As the death toll rises after a dam burst in Brazil, the quest for survivors has been halted after alarm bells signalled another possible disaster at the Vale mine.

The search for potential survivors of a dam collapse in Brazil has been suspended amid fears that another nearby dam owned by the same company was also at risk of breaching.

Authorities are evacuating several neighbourhoods in the southeastern city of Brumadinho that are within range of the B6 dam, owned by the Brazilian mining company Vale.

There was no immediate word on how many people were evacuated.

A spokesman for firefighters in Minas Gerais state Pedro Ahiara said the risk of the other dam breaking continues.

Nearly 300 people were missing at the last count, virtually all of them mine workers listed by Vale. Picture: Mauro Pimentel/AFPSource:AFP

Even before the latest news, hope that loved ones had survived a tsunami of iron ore mine waste from Friday’s dam collapse in the area was turning to anguish and anger over the increasing likelihood that many of the hundreds of people missing had died.

Company employees at the mining complex were eating lunch on Friday afternoon when the first dam gave way.

By Saturday night, when authorities called off rescue efforts until daybreak, the toll stood at 40 dead with up to 300 people estimated to be missing. All day Saturday, helicopters flew low over areas encased by a river of mud and mining waste as firefighters dug frantically to get into buried structures. Sonia Fatima da Silva, whose son had worked at Vale for 20 years, was trying to get information about him.

“I’m angry. There is no way I can stay calm,” she said.

“My hope is that they be honest. I want news, even if it’s bad.”

The flow of waste reached the nearby community of Vila Ferteco and an occupied Vale administrative office.